The present invention relates to a multi-axis robot for high-speed applications, and, more particularly, to a multi-axis robot comprising a first and a second guide rail arranged substantially parallel to each other for defining a first axis of motion, and a crossbar for defining a second axis of motion.
German patent application DE 44 44 523 A1 discloses a multi-axis robot using three belt drive systems for moving a tool carrier along three orthogonal axes X, Y, Z, and for rotating the tool carrier about one of these axes. The tool carrier is arranged on a carriage, which in turn is moveably supported on a crossbar. Each end of the crossbar is supported on one of two parallel guide rails. Therefore, the crossbar and the carriage provide for a movement of the tool carrier along two orthogonal axes, which are typically called X-axis and Y-axis. In order to move the carriage and the crossbar along these two axes, a drive system is provided which comprises two stationary motor drives and a continuous belt which runs along an H-shaped belt path. The H-shaped belt path matches the arrangement of the guide rails and the crossbar. If the two motor drives are driven both in the same rotary direction, the carriage is moved along the crossbar. If the two motor drives are driven in opposite rotary directions, the crossbar is moved along the guide rails.
In order to effect the movement of the tool carrier along the third axis and the rotation of the tool carrier around the third axis, two further H-shaped belts are provided. In summary, the known robot comprises three H-shaped belts which are arranged in parallel planes one above the other. An advantage of this robot design results from the stationary motor drives, with the drive forces being transferred to the tool carrier by means of the H-belts. The moveable part of the robot therefore does not need to carry the weight of the drives. Accordingly, the tool carrier can be made very lightweight, which allows highly dynamic movements with high accelerations and decelerations. Positioning accuracy, however, is limited with this known design, because the H-belt drive systems are susceptible to undesired rotations of the crossbar around its longitudinal axis and around the vertical Z-axis. Positioning inaccuracies resulting from such rotations may cause problems, in particular, if the tool carrier is moved very quickly, which should be a domain of this kind of robot design.
WO 97/02931 discloses further robot designs employing the H-belt approach. Again, however, the proposed designs are susceptible to positioning inaccuracies as a result of undesired rotations of the crossbar.
U.S. Pat. No. 4,976,582 discloses a completely different robot design, which is commonly known as Delta robot. The Delta robot also enjoys the benefit of stationary motor drives, which are configured to move a tool carrier via a parallel geometry. While this robot design also benefits from the low weight of the moving parts, it requires a sophisticated control logic in order to compute drive control signals from the desired movements of the tool carrier.
Beyond these two concepts, there are further robot designs, such as what is known as 6-axes-robot or what is called SCARA design. In order to allow movements along and around three or more axes, however, these robot designs require motor drives to be moved together with the tool carrier, which limits the dynamic behavior and/or requires high-power drive systems.